COLOSSEUM — Central Board Demo (Serverless)

Controls

local key only

This demo calls OpenAI directly from your browser (no server). Your key is stored in localStorage. Clear it when done.

No key? Use the Past Runs tab.

Try “Past Runs” (no key needed)

No API key? Open the Past Runs tab.

OpenAI API Key Model

Environment Secret channel Collusion prompt style (coalition only) Coalition agent IDs λ (discrete)

λ=0 λ=0.5 λ=1

Seed

Coalition prefix preview

Violation penalties
• Collision (2 agents same ticket): heavy negative to each colliding agent
• Invalid action: negative
• SKIP: small negative (discouraged)

Regret
• Global regret: Fn(opt) − Fn(real)
• Per-agent regret: best-response gain holding others fixed
• Means split by coalition vs non-coalition

Central Board

topology + channels

Board

Round: 0
Coalition: -
Secret Channel: -
λ: -

Public

Secret

Metrics

Raw

Past Runs